Ultrashort wave modulated carrier wave radio communication system



RB, A. A. LINSELL ULTRASHORT WAVE MODULATED CARRIER WAVE RADIO COMMUNIQATION SYSTEM Filed Jan. 13, 1934 2 Sheets-Sheet l INVENTOR ALFRED A. LINSELL ATTO RN March w, 193?. A, A, UNSELL mmmz ULTRASHORT WAVE MODULATED CARRIER WAVE RADIO COMMUNICATION SYSTEM Filed Jan. 13, 1934 2 Sheet s-Sheet 2 INVENTOR ALFRED A. LINSE LL ATTORN EY l atented Mar. 16, 1937 PATENT OFFIQE ULTRASHORT WAVE MODULATED CARRIER WAVE RADIO COMMUNICATION SYSTEM Alfred Aubyn Linsell, London, England, assignor to Radio Corporation of America, a corporation of Delaware Application January 13, 1934, Serial .No. 706,516 In Great Britain January 17, .1933

9 Claims.

This invention relates to ultrashort wave modulated carrier wave radio communication systems, and more particularly to modulated carrier wave radio systemsv wherein the wave length employed is in the range sometimes referred to as the quasi-optical rangei. e. centimeter waves, for example, waves of the order of 60 cm. Considerable difficulty is experienced in practice in modulating such, ultrashort waves in a sat- 10 isfactory manner; for example, in the usual methods .of applying modulation, e. g. in the method of anodemodulation, undesired changes in frequency are occasioned by the application of the modulating potentials.

The invention has for its primary object to provide a simple andreliable system wherein generation andtransmission of very high frequency wavesland also inodulationof the said highfrequency waves can be satisfactorily effected, substantially without affecting theoscillation generating or driving means. 7

According to thisfinvention, an ultrashortwave modulatedcarrier wave radio transmitting systern comprises thecombination of means for generating and radiating jjultrashort waves, one or more conductors interposed in the path of the radiatedwaves and means for varying the impedancejof 's'aid conductor or conductors in accordance with modulating frequencies whereby the 0 effect. of said conductor or conductors upon the radiated waves is varied.

It iswell known that if a conductive obstacle I be placedin the path of ultrashort waves, e. g. waves of the order of 60cm. or less, the radiation' willbe seriously obstructed if said obstacle be appropriately tuned relative to the working wave length and, therefore, in, carrying out the presentinventionit is proposed to placea conductorjwhose overall length may be equal to that 40 of an ultrashort wave radiator, in the path of the radiationtherefrom,"said conductor consisting of a j'plurality off conductor portions connected in series with one another 7 by the anode-cathode I space or spaces ofla valve or valves whose internal 5 impedance orjimp edances is or are controlled in potential byand/or in accordance with modulating potentials. If the bias applied to the grid or grids of the valve; or valves is suitably chosen,

it "is possible so to arrange matters that the conductor as a whole, i. 'e including the anode-cathode space or spaces of the valve or valves, is made substantially conductive. throughout its whole length during half cycles of modulation while during the other half cycles it will be equivalent 5s to twoor more sub-lengt (changing progres- I sively from one state to the other in dependence upon the low frequency modulation) and since these sub-lengths do not bear any direct relaticnship to the high frequency waves being transmitted, they will not affect the radiation to the same extent as. will occur when the conductor is substantially conductive over its whole length. As a result the outgoing waves will be modulated.

Preferably means are provided for preventing neutralizing carry-through effect of the modulating valve or valves at the very high frequencies concerned by reason of the internal self or interelectrode capacity thereof.

Preferably also the auxiliary conductor or conductors, i. e. the conductor or conductors by means of which modulation is effected, is or-are located at a distance exceeding one wave length from the radiator whose emission is to be modulated.

In carrying the invention into practice, induc tances of such value as to constitute chokes at V the working frequency should be placed in the high tension supply leads and filament leads of the valve or valves so as to confine the high frequency to the anode cathode path through the said valve or valves.

The invention is illustrated in and further explained in connection with the accompanying drawings, Figures 1 to '7 of which show various embodiments of the invention.

Referring to Figure l which shows, diagrammatically, one embodiment of the invention, there is provided an ultrahigh frequency radiator consisting of a dipole I, l, having a suitable ultrahigh frequency oscillation generating arrangement 2 connected to energize it centrally. .At a distance from this radiator exceeding one wave length, is an auxiliary conductor 3,, 3, consisting of two'conductive rodsor wires connected together by the anode-cathode space of a thermionic valve 4. The auxiliary conductor is thus, as it were a dipole with the anode-cathode space of the valve 4 arranged between the halves thereof, although it is not necessary that the two parts between which the valve is interposed be equal. The auxiliary conductor arrangement 3, 3, Al, is parallel to the radiator arrangement I, I, 2. Low frequency modulating potentials are applied through a radio frequency choke Ch between" the control grid and cathode of the valve and the initial bias thereon is so adjusted that for one low frequency half cycle the anode-cathode path is made moreconductive and for the other low frequency half cycle this path is made less conductive. Suitable steady potential is applied to the anode of the valve and the modulating potentials are applied to the grid thereof, for example, as indicated via a transformer T whose primary is connected to a microphone M (assuming speech modulation). For the sake of simplicity in the drawings, the sources of anode and grid bias potentials are omitted from Figure 1.

Preferably carry through effect of the valve f. at high frequency is neutralized-for example as shown in Figure 2by connecting between the anode and cathode of the valve 4 a nonradiating line 8 in series with a blocking condenser 9, the length of the line being such that any carry through effect at the high frequency and due to the valve capacity is neutralized. In Figure 2 the line 8 is caused to be substantially non-radiating by being bent back and forth upon itself.

In a further embodiment illustrated in Figure 3 the auxiliary conductor by which modulation is effected is divided into three portions connected in series by means of valves, there being thus two such valves 5 and 6. Each valve has its own grid transformer T1 or T2 the primaries of these transformers being connected for energization from a microphone M or other source of modulating potentials in any convenient way, e. g. in series therewith.

It is not necessary that the auxiliary conductor be simply of straight rod-like construction. For example, the above described embodiments may be modified by arranging the valve or valves to connect in series conductive portions consisting each of a plurality of rod-like members in parallel, e. g. as shown in Figure 4, which may be regarded as a variation of the arrangement of Figure 1, there may be three parallel rod-like members 3a, 3b, 30 connected to the anode of each valve and three similar parallel members, similarly designated connected to the cathode thereof. Of course, any desired suitable arrangement of conductive portions may be employed, the essential requirements being merely that the modulating potentials shall vary the effect of the whole conductor arrangement (whatever it may be) upon the transmitted waves.

In yet a further embodiment illustrated in Figure 5 two (or more) auxiliary conductors each consisting of two or more portions 3, 3, or 3', 3' connected together in series through a valve or valves 4 or 4 are provided, these auxiliary conductors being all in the path of the waves from the radiator I, l, but at different distances from said radiator. These auxiliary conductors which each include one or more valves 4 or 4' and are similar to one another, may be of the same length as the radiator length, and should be parallel thereto. Modulating potentials are applied to the valves of all the auxiliary conductors in suitable phase relationship, e. g. if the distance between two adjacent conductors is an even number of half wave lengths, the modulating potentials should be applied to the valves in said con ductors in phase, but if the distance between said conductors is an odd plurality of half wave lengths, the modulating potentials applied to the valves in one conductor should be 180 out of phase with the modulating potentias applied to the valves in the next.

In another method illustrated in Figure 6 of applying modulating potentials to a valve included in an auxiliary conductor employed in carrying out this invention, the modulating potentials are applied from H between grid and cathode of a low frequency amplifying valve I whose plate circuit includes the primary of a transformer H in series with a pair of high frequency chokes I2, I3, connected one on each side of said primary. The secondary of this transformer, may be shunted by a high frequency by-pass condenser l6 and is connected in series with the anode of the modulating valve 4 between said anode and the portion of rod-like condutor Which, in the previously described embodiments was directly connected to said anode. Anode potential is applied to the modulating valve 4 from a source HT1 via the secondary of the transformer and a suitable high frequency choke l4 in series, the negative terminal of the anode battery being connected to the common cathode point of the two valves I0 and 4 to which point the negative terminal of the anode battery HTz for the amplifying valve and the positive terminal of a negative grid bias battery GB for the modulating valve 4 are also connected.

In a modification-illustrated in Figure 7--of the last described embodiment the transformer coupling arrangement for the audio frequency valve I6 is replaced by a choke coupling arrangement. The anode of the audio frequency valve i0 is connected to the anode of the modulating valve 4 through a high frequency choke l1 and a low frequency choke l which may be shunted by a high frequency by-pass condenser 16 is connected in the position occupied in the last described embodiment by the secondary of the transformer. Thus both valves receive anode potential from a common source HT1.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is:

1. An ultrashort modulated carrier wave radio transmitting system comprising a transmitting aerial, means for energizing said aerial with unmodulated energy at an ultrashort wave length whereby said aerial radiates said energy, and an auxiliary conductor interposed in the path of the energy radiated from said aerial, said auxiliary conductor comprising two conductive portions connected together by a thermionic valve, and means for varying the internal impedance of said valve in dependence upon modulating potentials.

2. Apparatus as claimed in claim 1 and in which the transmitting aerial is a dipole.

3. Apparatus as claimed in claim 1 and in which the auxiliary conductor is parallel to the transmitting aerial and is located at a distance of at least one wave length therefrom.

4. An ultrashort modulated carrier wave radio transmitting system comprising a transmitting aerial, means for energizing said aerial with unmodulated energy at an ultrashort wave length whereby said aerial radiates said energy, and an auxiliary conductor interposed in the path of the energy radiated from said aerial, said auxiliary conductor comprising two conductive portions connected together by a thermionic valve, and means for varying the internal impedance of said valve in dependence upon modulating potentials, said conductive portions being each composed of a plurality of conductors in parallel.

5. An ultrashort modulated carrier wave radio transmitting system comprising a transmitting aerial, means for energizing said aerial with unmodulated energy at an ultrashort wave length whereby said aerial radiates said energy, and an auxiliary conductor interposed in the path of the energy radiated from said aerial, said auxiliary conductor comprising three conductive portions serially connected together through thermionic valves, and means for simultaneously varying the internal impedance of said valves in accordance with the message waves to be transmitted.

6. An ultrashort modulated carrier wave radio transmitting system comprising a transmittin aerial, means for energizing said aerial with unmodulated energy at an ultrashort wave length whereby said aerial radiates said energy, and an auxiliary conductor interposed in the path of the energy radiated from said aerial, said auxiliary conductor comprising two conductive portions, a thermionic valve having an anode, cathode, and a control electrode, oneof said conductive portions being connected to said anode and the other to said cathode, and means for applying modulating potentials to said control electrode.

7. An ultrashort modulated carrier wave radio transmitting system comprising a transmitting aerial, means for energizing said aerial with unmodulated energy at an ultrashort wave length 5 whereby said aerial radiates said energy, and an auxiliary conductor interposed in the path of the energy radiated from said aerial, said auxiliary conductor comprising two conductive portions, a thermionic valve having anode, cathode and con- 30 trol electrodes, one of said conductive portions being connected to said anode and the other of said portions being connected to said cathode, means for biasing said control electrode relative to said cathode, and means for applying modulating potentials to one of said electrodes of said valves for varying the internal impedance thereof.

8. An ultrashort modulated carrier wave radio transmitting system comprising a transmitting aerial, means for energizing said aerial with unmodulated energy at an ultrashort wave length whereby said aerial radiates said energy, and an auxiliary conductor interposed in the path of the energy radiated from said aerial, said auxiliary conductor comprising two conductive portions connected together by an electric discharge tube, and means for varying the internal impedance of said tube in dependence upon modulating signals.

9. In combination, means for generating energy at a radio frequency, means for radiating said energy, means for modulating said radiated energy in accordance with a signal, said last means comprising at least one conductor in the path of said radiated energy, an electric discharge tube having a continuously variable resistance discharge path, means for connecting said discharge tube in series with said conductor for continuously varying the resistance of said conductor, and means for causing the resistance of said discharge tube to vary in accordance with the wave form of said signal.

ALFRED AUBYN LINSELL. 

